Measuring saproxylic beetle diversity in small and medium diameter dead wood: The "grab-and-go" method

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Survey of selected beetle families in a floodplain remnant in northern Italy

Abstract The highly fragmented floodplain forest remnants of the river Po (Italy) are protected at the European level, but surprisingly little is known about their ecology and in particular their invertebrate fauna. The present work investigates 11 selected beetle families sampled in the reserve of Isola Boscone (Lombardy Region, Mantua Province), which is situated inside the embankments of the Po. Twelve window traps were attached to dead trees, either in open and sun-exposed situations (n = 6) or in the understorey of small forest patches (n = 6), and were active from 16 June to 3 November 2009. The following 11 beetle families were studied: Histeridae, Lucanidae, Scarabaeidae, Lissomidae, Elateridae, Buprestidae, Cleridae, Aderidae, Tenebrionidae, Cerambycidae, Anthribidae. A total of 495 individuals belonging to 53 species were collected, including five species of particular faunistic interest. The species Aegosoma scabricorne (Scopoli) and Dissoleucas niveirostris (F.) were associated with the forest habitat, while Chlorophorus varius (Muller), Dorcus parallelipipedus (L.) and Nalassus dryadophilus (Mulsant) were associated with the open habitat. Analyses of the abundance data revealed that the traps from the two habitat types differed in their community composition and that more species were caught in the open habitat. However, individual-based rarefaction curves showed that species richness did not differ when the number of species was plotted in relation to the number of individuals caught. This finding shows that richness estimates need to be interpreted with caution. The study also highlights that monitoring of beetles in floodplain forest remnants is complicated by recurrent floods

Ambient and substrate energy influence decomposer diversity differentially across trophic levels.

The species-energy hypothesis predicts increasing biodiversity with increasing energy in ecosystems. Proxies for energy availability are often grouped into ambient energy (i.e., solar radiation) and substrate energy (i.e., non-structural carbohydrates or nutritional content). The relative importance of substrate energy is thought to decrease with increasing trophic level from primary consumers to predators, with reciprocal effects of ambient energy. Yet, empirical tests are lacking. We compiled data on 332,557 deadwood-inhabiting beetles of 901 species reared from wood of 49 tree species across Europe. Using host-phylogeny-controlled models, we show that the relative importance of substrate energy versus ambient energy decreases with increasing trophic levels: the diversity of zoophagous and mycetophagous beetles was determined by ambient energy, while non-structural carbohydrate content in woody tissues determined that of xylophagous beetles. Our study thus overall supports the species-energy hypothesis and specifies that the relative importance of ambient temperature increases with increasing trophic level with opposite effects for substrate energy

Proposal for a time-based standard sampling method for the monitoring of Gomphus flavipes (Charpentier, 1825) and Ophiogomphus cecilia (Fourcroy, 1785) (Odonata: Gomphidae)

Monitoring of conservation status is an obligation arising from Article 11 of the Habitats Directive for all species of community interest. However, the development of monitoring methods for invertebrate species has received relatively little attention. Gomphus flavipes (Charpentier, 1825) and Ophiogomphus cecilia (Fourcroy, 1785) are two dragonfly species, listed in the annexes of the Habitats Directive, which suffered severe declines in the last century and have since recovered. Methods for the monitoring of these two gomphids have been proposed, but these have not been extensively tested and no abundance classes have been proposed for the evaluation of the conservation status of these species. A time-based standard sampling method is proposed for both species and results from numerous sites in Lombardy, northern Italy, are presented. Applying the standard method revealed that it is common for rivers that high water levels preclude sampling of exuviae through the summer and it is better to allow for two seasons when planning the monitoring. A further result is the fact that it was not always possible to sample the same stretches as the dynamic nature of the rivers and fluctuations in water level lead to some river banks becoming unsuitable for sampling during some visits. In these cases the time-based approach was advantageous, as the method did not need to be modified in response to the original bank section becoming unsuitable

Does wing shape of andromorph females of Calopteryx splendens (Harris, 1780) resemble that of males?

Female limited polymorphism consists in the coexistence of two or more female morphs in the same population and is widespread among odonates. Generally, one female morph, the andromorph, resembles males in colour or, sometimes, also in morphology and behaviour, while one or more other morphs, gynomorphs, differ from males. This phenomenon is probably promoted by advantages to females which arise from reduced sexual harassment. Andromorph females of Calopteryx splendens keep wing spots, like males (although these ornaments do not match exactly male wing spot colour), while gynomorphs have hyaline wings. Males and gynomorphs show a marked sexual dimorphism in wing shape, and this determines flight patterns which differ between sexes. If andromorphs mimic male wing spots to avoid harassment, they may also benefit from mimicking the male flight morphology, and consequently the male flight pattern. In this case wing shape of andromorph and gynomorph females would differ, as the wing shape of andromorphs resembles that of males. In this study we compared the wing morphology of males and of the two female morphs of C. splendens using geometric morphometrics. Our results revealed that andromorphs and gynomorphs of this species share the same wing shape, size, and static allometry, and this suggests that flight patterns should also be shared by the two morphs. Thus, females might avoid male harassment by mimicking exclusively male wing pigmentation (male mimicry hypothesis), or confound males through an uncommon appearance (learned mate recognition hypothesis)

Odonates as indicators of the ecological integrity of the river corridor: Development and application of the Odonate River Index (ORI) in northern Italy

none4noThe assessment of the ecological conditions of rivers is crucial for their appropriate management andrestoration. Bioindicators commonly used to evaluate the river status (i.e. diatoms, aquatic macrophytes,benthic macroinvertebrates and fish) detect alterations of water quality, but are not particularly sensitiveto hydromorphological degradation, which is another relevant pressure in river systems. Furthermore,those bioindicators are usually applied only to flowing channels. We developed a new multimetric index,the Odonate River Index (ORI), to assess the conditions of the whole corridor in alluvial rivers. The ORIis a development of an evaluation system proposed in Austria, and based on the Odonate Habitat Index(OHI). Odonates were chosen as bioindicators for the ecological integrity of the river corridor, since thistaxon provides information on the conditions of their aquatic breeding sites, as well as on the surroundingterrestrial areas, due to its amphibiotic life cycle. We used a case study of 18 reaches from six Italian Alpinerivers, characterized by different morphological conditions and level of human impact. Within each studyreach, we selected four sites, both lotic and lentic sites. Dragonfly surveys consisted in field observationof adults, and collection of larvae and exuviae. To define the best sampling strategy, we compared theresults of the ORI metrics obtained varying the input data by combining different sampling methods: thebest compromise between effort and exhaustiveness was obtained coupling the observation of adultswith the collection of exuviae. We found the ORI to be a robust and reliable tool to assess the status ofthe river corridor in a wide range of environmental conditions and river morphology, being particularlysuitable to detect hydromorphological degradation and alterations of the structure of aquatic and riparianvegetation. We identified two limiting factors for the applicability of this index: low water temperaturesof the main channel (i.e. mean annual value below 10◦C) and river reaches with no or scarce aquatic andriparian vegetation. In addition to the assessment of river conditions, the ORI could also be applied formonitoring the effects of river restoration actions.noneGolfieri, Bruno; Hardersen, Sönke; Maiolini, Bruno; Surian, NicolaGolfieri, Bruno; Hardersen, Sönke; Maiolini, Bruno; Surian, Nicol

Season matters: differential variation of wing shape between sexes of Calopteryx splendens (Odonata: Calopterygidae)

Insects adapt commonly to seasonally changing habitats and reproductive contexts. Individuals that mature at different times during the year can show patterns of life cycle or morphological variation, possibly associated with changes in reproductive behaviour. Concerning mating strategies of flying insects, wing morphology may be related both to the outcome of male–male contests and to the ability in acquiring females. Therefore, different mating strategies (territorial vs. non-territorial) may have different flight morphology optima that increase fitness in their context. Males of Calopteryx splendens are mainly territorial early in the season, but with the advancing season and with increasing competition, more and more males adopt a non-territorial pursuing strategy. Given that different mating tactics have different wing morphologies, here we test whether the wing shape of males shifts from a ‘‘territorial’’ to a ‘‘non-territorial morphology’’ during the season. So, early in the season males show highly sexually dimorphic wings, which allow for high manoeuvrability and larger spots, while late in the season wing shapes of males become less sexually dimorphic and more suitable when pursuing females. Additionally, we studied the seasonal variation of other flight related traits, specifically wing lengths, abdomen length and weight. We found that these latter traits decreased along the season in both sexes without altering sexual dimorphism. However, wing shape, which resulted sexually dimorphic, showed a seasonal variation, decreasing the level of sexual dimorphism. The most probable determinant of this change is phenotypic plasticity triggered by environmental cues, but other explications of the observed pattern are discusse

Composition and Stratification of a Tachinid (Diptera: Tachinidae) Parasitoid Community in a European Temperate Plain Forest

. 1. We analysed the canopy and understorey communities of flies in the family Tachinidae, the most diverse group of parasitoid Diptera, in a small and isolated temperate plain forest in northern Italy. Our objective was to assess whether and how these communities differ from one another, and how species distribution relates to forest structure, host distribution, mating sites, and season. 2. The study was carried out in 2008 with 14 Malaise traps installed between April and November in an equal number of sites randomly selected inside the forest, seven on the ground and seven in the tree canopy. 3. Overall species richness, abundance, and turnover were greater in the understorey traps, but most diversity metrics indicate greater overall diversity and evenness in the canopy traps. Community ordination and estimates of beta diversity indicate that the two habitat-associated communities are distinct and should both be considered in assessments of insect diversity and community structure. Indicator species values revealed the presence of a number of species that were effective indicators of canopy and understorey habitats. No strong male bias in canopy traps was observed across species; however, the only significant sex ratio biases in the canopy were towards males. Both male and female biases were observed in understorey traps, depending upon the species

Sexual dimorphism in wings and wing bands of Sympetrum pedemontanum (Müller in Allioni 1776)

Sexual dimorphism is common in animals and derives from two mechanisms: sexual selection and sexual niche divergence. These mechanisms may work together as determinants of wing shape in pigmented wings of Odonata. On the one hand, sexual selection by females tends to enlarge the wing areas of males that host pigments; on the other hand, sex-specific flight behaviours, due to differential niche selection, may promote sexual dimorphism. Both sexes of Sympetrum pedemontanum have ornamented wings with bands, but their function is poorly understood. Therefore, we studied shape and size of wings and wing bands of S. pedemontanum using geometric morphometrics to quantify the extent of sexual dimorphism. We also investigated whether sexual dimorphism in wing shape derives from the effect of sexual selection on wing ornamentation or from sexual niche separation. We found sexual dimorphism in wing shape and in the shapes of the bands, but the absence and misdirection of sexual size dimorphism and wing shape dimorphism of bands do not support the hypothesis that wings and wing bands in S. pedemontanum are subjected to sexual selection. Instead, the pattern of sexual dimorphism in wing shape seems more likely to be caused by sex-specific flight requirements

Composition and Stratification of a Tachinid (Diptera: Tachinidae) Parasitoid Community in a European Temperate Plain Forest

. 1. We analysed the canopy and understorey communities of flies in the family Tachinidae, the most diverse group of parasitoid Diptera, in a small and isolated temperate plain forest in northern Italy. Our objective was to assess whether and how these communities differ from one another, and how species distribution relates to forest structure, host distribution, mating sites, and season. 2. The study was carried out in 2008 with 14 Malaise traps installed between April and November in an equal number of sites randomly selected inside the forest, seven on the ground and seven in the tree canopy. 3. Overall species richness, abundance, and turnover were greater in the understorey traps, but most diversity metrics indicate greater overall diversity and evenness in the canopy traps. Community ordination and estimates of beta diversity indicate that the two habitat-associated communities are distinct and should both be considered in assessments of insect diversity and community structure. Indicator species values revealed the presence of a number of species that were effective indicators of canopy and understorey habitats. No strong male bias in canopy traps was observed across species; however, the only significant sex ratio biases in the canopy were towards males. Both male and female biases were observed in understorey traps, depending upon the species